Chemical Composition and Broad-Spectrum Insecticidal Activity of the Flower Essential Oil from an Ancient Sicilian Food Plant, <i>Ridolfia segetum</i>

Several species of the family Apiaceae are aromatic herbs that produce essential oils usable on an industrial scale for pharmaceutical, cosmetic, and food purposes. In particular, some essential oils, such as green insecticides for example, may replace synthetic insecticides, keeping most of their efficacy and avoiding environmental pollution or human poisoning. In the present study, we explored the insecticidal potential of <i>Ridolfia segetum</i> (L.) Moris essential oil (EO) against three different pests: <i>Culex quinquefasciatus</i> Say, <i>Musca domestica</i> L., and <i>Spodoptera littoralis</i> (Boisduval). For this purpose, the EO was obtained by hydrodistillation of flowers and its composition was achieved by gas chromatography/flame ionization detection (GC/FID) and gas chromatography/mass spectrometry (GC/MS). This EO was rich in <i>α</i>-phellandrene (49.3%), <i>β</i>-phellandrene (9.2%), terpinolene (20.7%), and piperitenone oxide (5.9%). Concerning the mosquitocidal efficacy, the EO showed noteworthy toxicity against <i>C</i>. <i>quinquefasciatus</i> 3rd instar larvae, with a LC₅₀ = 27.1 µL L⁻¹ and LC₉₀ = 42.5 µL L⁻¹. Regarding <i>M</i>. <i>domestica</i>, a different toxicity of the <i>R</i>. <i>segetum</i> EO was found on male and female flies, calculating LD₅₀ values of 10.5 and 50.8 µg adult⁻¹, respectively. The EO was also toxic to <i>S</i>. <i>littoralis</i> 3rd instar larvae, achieving LD₅₀ and LD₉₀ values of 37.9 and 99.6 µg larva⁻¹, respectively. Overall, this flower EO, extracted from a traditional Sicilian food plant, merits further investigation for the development of green insecticide formulations to be used in real world conditions, pending a careful assessment of non-target toxicity on beneficial organisms.